| 摘要 |
A state in which no voltage is applied between a pair of electrodes, or a state in which the potential difference between a pair of electrodes is less than a reference value, is induced for a predetermined period before the output of a 1-cell type NOx sensor is detected. The "reference value" for the potential difference between the electrodes can be set as appropriate within a range smaller than at least the voltage for output detection, and is 0V or a small potential difference in the vicinity of 0V. An amount of NOx is thereby caused to accumulate on the electrodes of the NOx sensor. After the predetermined period has elapsed, a voltage for sensor output detection is applied between the electrodes. The NOx concentration is detected according to the sensor output once the voltage for sensor output detection has been applied. |
